As summer approaches, effort to stop oak disease continues

With the weather warming up, trees around the state will soon fill with leaves again.

But not for some red oak trees in the state.

Oak wilt, an invasive fungal disease that can easily kill red oak trees, has spread to trees across the state, mainly in northern Michigan. Once infected with oak wilt, red oak trees die within three weeks of infection — and there’s no treatment for the disease once it has spread.

“Oak wilt is probably one of the largest diseases I’ve been dealing with as a forester, and have been dealing with for quite some time,” said Kama Ross, district forester for Leelanau, Benzie and Grand Traverse conservation districts.

The oak wilt infection occurs when fungus spreads through the roots of a healthy tree, and can be spread to trees around it through connecting root systems. The disease can also be transmitted by beetles, which can carry the oak wilt pathogen after they feed the sap from on infected trees.

The disease can also spread by moving infested firewood.

Bob Heyd, a forest health specialist with Michigan's Department of Natural Resources, told Michigan Radio the disease is quite infectious.

“It’s not really fast-moving, but as it goes from tree to tree, more trees have it and it will spread to more trees. It’s something you want to react to as quick as you can," Heyd said.

While the department is working to detect all cases of oak wilt, Heyd says just “because we haven’t detected it doesn’t mean it’s not there.”

Red oaks play a valuable role in Michigan as an important part of a habitat for the acorns it produces. Additionally, according to Michigan’s Department of Natural Resources, red oak timber is worth approximately $1.6 billion in the state.

Ross said looking into this issue specifically made her realize how interconnected ecosystems and habitats are, and how vital each part of them is.

“I just am now starting to get it — just how interrelated everything we currently have in our world is and how important we need to think about those things that we don’t necessarily see,” Ross said.

She pointed to how the red oaks serve as a valuable habitat for insects, a vital part of a food chain. Basically, if the red oaks are hurt by this disease, the surrounding habitat will suffer with it.

“We need to be good stewards of the land, and oak wilt is one of those that we do have some control over if we do actually get it,” Ross said.

While the infected red oaks are untreatable, both Heyd and Ross recommended ways to prevent the spread of the disease:

Leave trees alone. To prevent further infection across the state, Michigan’s Department of Natural Resources advises residents to not prune oak trees between April 15 and July 15 — the peak growing season for the red oaks. Pruning means cutting off any parts of the tree or exposing any sap — which oak wilt-carrying beetles are attracted to.

Don't move your firewood. Oak wood can be spread by the movement of the infected wood.

Diversify your woods. Ross says she has told residents of her district to consider planting other kinds of oak trees — which are not as susceptible to the disease — to break up the types of roots capable of spreading the disease to other trees around it.

Perhaps the most important thing to know? Oak wilt isn't going away any time soon.

“It’s not going to go away, so if you get a new outbreak of oak wilt, just letting it be is not an answer,” Ross said.

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